Synthesis, Characterization and Antimicrobial Activity of Cu(II),Co(II), Ni(II) and Zn(II),Complexes with O-N donor ligand.

 

Y.KGupta¹*, Vinita Gupta², Sanchita Singh²

¹Head Department of Chemistry, B K Birla Institute of Engineering and Technology, Pilani, Rajasthan, India

²Department of Chemistry, Agra College, Agra, U.P, India

 

 

ABSTRACT:

The complexes of the type MLXn, where M= Cu(II), Co(II), Ni(II), Zn(II) and X= H₂O/Cl and L is the schiff base ligand prepared from 2,4-dihydroxy-5-Acetylacetophenone and 1,4-diaminobutane have been synthesized. All complexes isolated in solid, are stable in air and characterized by the elemental analysis, metal content determination, magnetic measurements, thermo gravimetric analysis (TGA), IR, and electronic spectral data. The physicochemical data suggest a pseudo octahedral structure to Cu(II) and an octahedral for Co(II), Ni(II), and Zn(II) complexes. The ligand field parameters have been calculated and related to the electronic environment. The Schiff base and its complexes were screened for their antimicrobial activities against various bacteria and fungi.

 

 

INTRODUCTION:

Schiff bases are widely used as chelating ligands in coordination chemistry and investigated extensively for the last several decades leading to new synthetic routes of structure, biological and industrial applications [1-3]. They are also useful in catalysis and in medicine as antibiotics, anti allergic and antitumor agents [4-6]. Schiff base complexes with Cu(II), Co(II), Ni(II) and Zn(II) metal ions [7-10] have been found to exhibit good physiological and pharmacological activities. However, metal complexes of Schiff base of 2, 4-dihydroxy -5-acetylacetophenone and 1, 4 diaminobutane have not been investigated. Hence, it was the interest to carry out systematic investigation on Cu(II), Co(II), Ni(II) and Zn(II) complexes of Schiff base prepared from 2,4-dihydroxy -5-acetylacetophenone and 1,4 diaminobutane.

 

EXPERIMENTAL:

Physical measurements

Elemental analysis of all the samples was carried out at CDRI, Lucknow. The metal contents were estimated after decomposition of the complexes with concentrated H₂SO₄ and HNO₃ as per procedures [11]. Magnetic susceptibility measurements were made on Gouy’s balance at room temperature with Hg [Co(SCN)₄] as a calibrant and the diamagnetic corrections were made using Pascal's constant. The spectra of the complexes were recorded on varian Cary-5E UV-visible spectrophotometer at SAIF, ¹HNMR spectra of ligand (CDCl₃+DMSO) was recorded on a NMR-JEOL GSX-400 spectrophotometer and chemical shifts are indicated in ppm relative to tetramethylsilane. Infrared spectra of the ligands and their complexes were obtained in KBr pellets on a Perkin-Elmer spectrometer at SAIF, Chandigarh. Thermogravimetric analyses (TGA) of complexes were performed on a TGS-2 Perkin-Elmer thermal analyzer in an ambient air with a heating rate of   10 ⁰C min^-1. The ligands and their metal complexes were screened for antimicrobial activity against E.Coli, S.Typhi, P. aeruginosa and S.aureus by cup plate method.

 

Received on 11.11.2014            Accepted on 20.12.2014      © EnggResearch.net All Right Reserved Int. J. Tech. 4(2): July-Dec. 2014; Page 283-286

Materials

All the chemicals and solvents used were of analytical grade. cobalt(II) acetate tetrahydrate, copper(II) acetate monohydrate, nickel(II) acetate tetrahydrate, zinc(II) acetate dihydrate, were obtained from S.D’s. fine Ltd, India

 

Synthesis of Schiff base ligand 2, 4-dihydroxy-5-acetylacetophenone with 1,4 –diaminobutane (L)

The Schiff base was synthesize in two steps, In first step, preparation of 2, 4-dihydroxy -5-acetylacetophenone and in second step, condensation of the acetophenone with 1-4 diaminobutane have been made.

 

Fig. 1. Schiff base ligand 2,4-dihydroxy-5-acetylacetophenone with 1,4 –diaminobutane (L)

 

Step I: Preparation of 2, 4- dihydroxy - 5-acetyl acetophenone

The acetophenone were prepared by refluxing (5 gm 0.05 mol) of resorcinol and (9ml, 0.05mol) acetic anhydride was taken in a 100 ml of round bottom flask for 45 minutes in presence of fused zinc chloride (7gm) the mix was allowed to cool at room temperature and them prepared on crushed ice with vigorous shaking. A radish brown precipitate separated out. It was filtered and boiled in water for 15 minutes. The boiling solution was filtered in hot condition the precipitate so obtained was washed with hot water, recrystallized from distilled ethanol and dried in vacuum.

 

Step II: Condensation of the 2, 4-dihydroxy-5-acetylacetophenone with 1,4 –diaminobutane

1,4-diaminobutane (0.05 mol) was added drop wise to an ethanolic solution of 2, 4- dihydroxy - 5-acetyl acetophenone (0.05 mol in 25 ml ethanol) in round bottom flask with continuous stirring. The reaction mixture was heated under reflux for about 3-4 hr. After cooling to room temperature a colored product formed was filtered, washed with ethanol, dried at room temperature and finally crystallized from hot ethanol. Yield 65% m.p. 170⁰C.

 

¹HNMR of 2, 4-dihydroxy-5-acetylacetophenone with 1,4 –diaminobutane (L)

The ¹HNMR spectrum of ligand exhibits signal at δ 8.00 due to imine proton. The aromatic protons are observed in the range δ 7.35 - 7.65 (2H, s, phenyl), the phenolic OH appeared at δ 12.20 (2H, S, Phenolic OH), δ 3.10 (4H, t, N, CH₂), δ 1.90 (4H, m, CH₂), δ 2.6 (6H, s, methyl).

 

Synthesis of the complexes

All the metal complexes were prepared by a following general method: Equimolar (1.00mmol) quantities of appropriate metal salts and ligand 2, 4-dihydroxy-5-acetylacetophenone with 1,4 –diaminobutane (L) were dissolved separately in minimum quantity (25-30 ml) of DMF. Both solutions were filtered and then mixed in hot condition with constant stirring. The reaction mixture was refluxed on a sand bath for a 3-4hr. The resulting coloured product obtained was filtered, washed several times with DMF followed by acetone to remove unreacted ligand and metal salt. Finally, the complexes were dried in vacuuo over anhydrous CaCl₂. Yield: 60-70 %.

 

RESULTS AND DISCUSSION:

All the complexes are coloured solids, air stable and insoluble in water and common organic solvents but found soluble in DMF and DMSO. The analytical data indicate 1:1 metal: ligand stoichiometry for all the complexes (Table 1).

 

Table 1. Analytical data of 2,4-dihydroxy-5-acetylacetophenone with 1,4 –diaminobutane  (L) and its Complexes

S.N.	Compound	Weight Formula (gmol-1)	Colour	Time of Reflux (hr.)	Elemental analyses % found (calcd.)
					M	C	H	N
1.	L	393.55	Yellow	3	--	66.93 (66.99)	6.35 (6.48)	12.01 (12.11
2.	[Cu(L)2H2O]	453.85	Raven Song	10	12.48 (12.49)	52.00 (52.01)	3.86 (3.97)	5.42 (5.51)
3.	[CO(L)2H2O]	449.35	Grayish brown	8	11.59 (11.70)	52.46 (52.48)	3.95 (4.00)	5.41 (5.56)
4.	[Ni(L)2H2O]	449.11	Sapphire ice	9	11.50 (11.66)	52.48 (52.51)	4.00 (4.01)	5.45 (5.57)
5.	[Zn(L)2H2O]	455.80	Lemon Pie	12	12.70 (12.82)	51.72 (51.82)	3.80 (3.95)	5.38 (5.49)

 

 

The infrared spectrum of ligand exhibits a broad band at 2935 cm^-1 due to presence of intramolecular hydrogen bonding between phenolic OH and azomethine nitrogen atoms [12]. This band is absent in spectra of complexes thereby suggesting the coordination of ligand to metal ion through the loss of phenolic proton on complexation. The ν C-O (phenolic) band in complexes is shifted to higher energy by ≤ 15-33 cm^-1, which indicates the coordination of the phenolic oxygen atom [13]. The ligand spectrum exhibits a strong band at 1610 cm^-1 due to C=N stretching frequency which on coordination is shifted to lower frequency by 22-40cm^-1 in the spectra of all complexes .The lowering may be due to a reduction in the electron density in the azomethine link [14] which indicate coordination to metal ion through azomethine nitrogen, it is further supported by the amino nitrogen and the phenolic oxygen are involved in the complexation with the metal ion which is clearly evident from the appearance of new medium intensity band in the region 590-654 cm^-1 and 450-495 cm^-1 assignable to M-O and M-N bands respectively [15]. The medium broad band and strong bands in the Cu(II), Co(II), Ni(II), Zn(II) and Cd(II) in the region 3413-3440 cm^-1 due ν(OH), and a strong sharp band 835 cm^-1 due to the (H₂O) rocking and waging modes suggests these water molecules as coordinated one [16].

 

On the basis of above IR data (Table 2) thus it may be concluded that ligand (L) behave as a dibasic tetradentate ligand coordinating through deprotonated phenolic Oxygen and azomethine Nitrogen atom.

 

Table 2. IR Analysis (cm^-1) of the Ligand (L) and its Metal Complexes

S.N.	Compound	ν(O-H)	ν (C=N)	ν (C-O)	ν (M-O)	ν (M-N)	ν (H2O)
1.	L	2934	1609	1274	--	--	--
2.	[Cu(L)2H2O]	--	1572	1305	652	494	3427,850,1641
3.	[CO(L)2H2O]	--	1573	1306	541	450	3440,844,1637
4.	[Ni(L)2H2O]	--	1570	1297	651	490	3427,832,1642
5.	[Zn(L)2H2O]	--	1575	1298	632	491	3418,834,1630

 

 

The magnetic moment of Cu (II) complex is found to be 1.89 B.M. suggesting distorted octahedral geometry. The Cu (II) complex shows bands at 17006-17301, 19074-19455 and 20408-20920 cm^-1 due to ²B_1g  → ²A_1g, ²B_1g  → ²B_2g and ²B_1g  → ²E_g ,transitions ,respectively, towards Pseudo octahedral structure around Cu(II) ion [17].

 

The Co(II) complex shows magnetic moment 4.75 B.M. suggest high spin octahedral geometry for Co(II) complex . The electronic spectrum Co(II) complex shows three bands in the regions 7704-7812, 10050-9881 and 16129-16722 cm^-1 assignable to ⁴T_1g  → ⁴T_2g(F), ⁴T_1g  → ⁴A_2g (F) and ⁴T_1g  → ⁴A_1g (P),transitions, respectively, in an octahedral environment around the cobalt ion. Ligand field parameters for Co(II) complex have been calculated by using standard equation  [18] and values are found. The reflectance spectral parameters for Co(II) are found to be Dq=1631.3cm^-1, B= 569cm^-1, β = 0.619 and % covalency= 38.1.

 

The magnetic moment of Ni(II) complex is 2.86 B.M. which lies in the normal range of octahedral Ni(II) complexes. The electronic spectrum of Ni(II) complex exhibits three bands at 10329-10559 , 16977-17543 and 24875-25188 cm^-1. These bands may be assigned to the transitions ³A_2g  → ³T_2g, ³A_2g (F)  →³T_2g and ³A_2g  → ³T_1g, (P), respectively in octahedral configuration [19, 20]. The Zn(II) complexes are found diamagnetic as expected from their electronic configurations.

 

Thermal analyses of the complexes were carried out upto 700⁰C. All the complexes show a gradual mass loss indicating decomposition by fragmentation with increase in temperature and follow the similar pattern of their thermal decomposition. The complexes remains unaffected up to 60⁰C after this a slight depression is observed up to 120⁰C. The weight loss at this temperature range is corresponds to two water molecules for Co(II), Ni(II) and Zn(II) complexes. After the loosed of coordinated water, anhydrous complexes remain stable for a while at 320⁰C and thereafter again the complexes show rapid degradation presumably due to decomposition of organic constituent of the molecules as indicated by the steep fall in the percentage of weight loss and continued up to 620⁰C . TG curves show continuous mass loss in a temperature range 320 – 650 ⁰C and attain a horizontal level above 650⁰C suggesting the formation of final decomposition product as stable metal oxides [21, 22].

 

Antimicrobial activity was carried out by the cup plate method [23, 24]. The ligand Land its Cu(II),Co(II),Ni(II) and Zn(II) Complexes have been screened for their antimicrobial activities at 100 μg/0.1cm³ concentration. The inhibition effect of ligands and their metal complexes on growth of various bacteria is summarized in Table 3.

 

Table 3. Antimicrobial activity ligand and its complexes (mm)

S.N.	Compounds	E. Coli	S. Typhi	P. aeruginosa	S.aureus
1.	L	15	16	12	16
2.	[Cu(L)2H2O]	11	12	R	14
3.	[CO(L)2H2O]	14	12	10	15
4.	[Ni(L)2H2O]	15	14	11	16
5.	[Zn(L)2H2O]	12	R	12	17

 

The growth of E. coli and S. aureus is more inhibited by almost all the compounds as compared to other bacterial species. The Cu(II)and Co(II)  are highly active against S. aureus whereas Ni(II) and Zn(II)are found to show good activity against E.Coli. All the compounds are either resistant or weak to moderately active and low sensitive against P.aeruginosa and S. typhi [25].

 

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Received on 25.10.2014            Accepted on 22.11.2014      © EnggResearch.net All Right Reserved Int. J. Tech. 4(2): July-Dec. 2014; Page 265-282